Arylazo-hydroxy pyridone dyes containing a pyridinium group

ABSTRACT

Azo dyestuffs devoid of carboxylic acid and sulphonic acid groups and of the formula (I) ##STR1## wherein R is a hydrogen atom, halogen atom, cyano, nitro, hydroxy or amino group or an organic radical, R 1  is a hydrogen atom, an optionally substituted hydrocarbon or heterocyclic radical or an amino group which may be substituted, Y is a group --OCOR 2 , --OSO 2  R 2  or --NHSO 2  R 2  wherein R 2  is optionally substituted alkyl or aryl, K⊕ is a cationic group, X⊖ is an anion and the ring A may carry further substituents or have a benz ring fused thereon. Manufacture of such dyestuffs and use in the dyeing of synthetic polymeric materials.

This invention relates to new water-soluble azo dyestuffs, to their manufacture and to the use of such dyestuffs for the colouration of synthetic polymeric materials in the form of ribbons, tapes, fibres, films, threads and textile materials generally. The dyestuffs are particularly valuable for the colouration of polymers and copolymers of acrylonitrile and of dicyanoethylene and also acid-modified polyesters and polyamides.

According to the present invention there are provided azo dyestuffs devoid of carboxylic acid and sulphonic acid groups and of the formula (I) ##STR2## wherein R is a hydrogen atom, halogen atom, cyano, nitro, hydroxy or amino group or an organic radical, R¹ is a hydrogen atom, an optionally substituted hydrocarbon or heterocyclic radical or an amino group which may be substituted, Y is a group --OCOR², --OSO₂ R² or --NHSO₂ R² wherein R² is optionally substituted alkyl or aryl, K⁺ is a cationic group, X⁻ is an anion and the ring A may carry further substituents or have a benz ring fused thereon.

The azo dyestuffs of the invention can exist in a number of tautomeric forms; for convenience the dyestuffs have only been formulated in one of these tautomeric forms, but it is to be understood that this invention includes within its scope the dyestuffs in any of the possible tautomeric forms.

R may be a hydrogen atom, halogen atom, cyano, nitro, hydroxy or amino group or an organic radical, examples of such organic radicals including optionally substituted alkyl, aryl, aralkyl, cycloalkyl and heterocyclic radicals, carboxylic acid ester and carboxylic acid amide, substituted amino and hydrocarbyloxy groups.

Specific examples of R include methyl, ethyl, n-propyl, n-butyl, β-hydroxyethyl, β-methoxy (or ethoxy)-ethyl, β-cyanoethyl, carbethoxymethyl, acetylmethyl, phenyl, chlorophenyl, methoxyphenyl, benzyl, phenylethyl, cyclohexyl, 2-pyridyl, 2-thiazolyl, 1-piperidyl, 2-morpholinyl, methoxycarbonyl, ethoxycarbonyl, carbamyl, N,N'-dimethylcarbamyl, N,N'-diethylcarbonamido, chloro, cyano, nitro, amino, hydroxy, bromo, methoxy, ethoxy, diethylamino, N-methyl-benzylamino, N-methylanilino, anilino, methoxycarbonylmethyl, methylsulphonylmethyl, anilinocarbonylmethyl, cyanomethyl, N,N-dimethylaminocarbonylmethyl, N-nonylcarbamyl, nonloxycarbonyl, N-phenylcarbamyl, N-benzylcarbamyl, N,N-dibenzylcarbamyl, 2-furyl, 2-thienyl, 2-pyrryl and phenoxymethyl.

R¹ may be a hydrogen atom, an optionally substituted hydrocarbon or heterocyclic radical or an amino group which may be substituted.

Specific examples of R¹ include methyl, ethyl, n-propyl, n-butyl, β-hydroxyethyl, β-methoxy (or ethoxy)-ethyl, β-cyanoethyl, carbethoxymethyl, γ-methoxypropyl, acetylmethyl, phenyl, tolyl, chlorophenyl, methoxyphenyl, benzyl, phenylethyl, cyclohexyl, 2-pyridyl, 2-thiazolyl, 1-piperidyl, 1-morpholinyl, dimethylamino, 2-ethylhexyl, nonyl, dodecyl, p-butylphenyl and p-dodecylphenyl.

Y may be a group of the formula --OCOR², --OSO₂ R² or --NHSO₂ R² wherein R² is an optionally substituted alkyl or aryl group. For example when R² is methyl, Y may be acetyloxy, methyl sulphonyloxy or methyl sulphonamido.

Specific examples of Y as --OCOR² include acetyloxy, propionyloxy, butyryloxy, valeryloxy, benzoyloxy, caprylyloxy, capryloxy, lauryloxy, myristyloxy, palmityloxy, stearyloxy, cinnamoyloxy, benzylcarbonyloxy, p-nitro benzoyloxy, p-methylbenzoyloxy and p-chlorobenzoyloxy, as --OSO₂ R², methyl sulphonyloxy, ethylsulphonyloxy, phenylsulphonyloxy, p-tolylsulphonyloxy, butyl sulphonyloxy, hexlsulphonyloxy, nonylsulphonyloxy, dodecylsulphonyloxy and hexadecylsulphonyloxy, and as --NHSO₂ R² methylsulphonamido, ethylsulphonamido, hexylsulphonamido, phenylsulphonamido, nonylsulphonamido, dodecylsulphonamido, hexadecylsulphonamido, p-toluenesulphonamido and phenylsulphonamido.

The group Y is preferably in the para position relative to the azo group. Preferably R² is an alkyl group of more than 5 carbon atoms.

As examples of cationic groups which are represented by K⁺ are included quaternary ammonium, cycloammonium, hydrazinium, sulphonium, isothiouronium, etherified hydroxylammonium and phosphonium groups which may be associated with any anion X⁻.

As quaternary ammonium groups are meant groups of the formula ##STR3## wherein R³, R⁴ and R⁵ represent optionally substituted alkyl or cycloalkyl groups or one may be a phenyl group or wherein R⁴ and R⁵ taken together with the nitrogen atom form a 5 or 6 membered ring.

As optionally substituted alkyl groups R³, R⁴ and R⁵ there may be mentioned methyl, ethyl, benzyl, cyclohexyl and β-hydroxyethyl.

As 5 or 6 membered rings which may be formed from R⁴ and R⁵ together with the nitrogen atom there may be mentioned piperidine and morpholine (as in piperidinium and morpholinium salts), in this case the group R³ is optionally substituted alkyl or cycloalkyl. These latter can also be described as cyclammonium groups. As cyclammonium groups there are meant heterocyclic systems containing in the ring a quaternised nitrogen atom which is preferably the point of attachment of the ring to the remainder of the molecule, for example N-methylpiperidinium and N-methylmorpholinium, but more particularly aromatic heterocyclic quaternary systems such as pyridinium, α-picolinium, β-picolinium, γ-picolinium, quinolinium, iso-quinolinium, and including heterocyclic systems containing heteroatoms additional to the quaternised nitrogen atom and substituted derivatives of the foregoing.

As sulphonium groups there are meant groups of the formula ##STR4## wherein R⁶ stands for an alkyl or substituted alkyl radical such as methyl or ethyl, R⁷ stands for an alkyl or substituted alkyl radical such as methyl, ethyl, and δ-hydroxyethyl, a cycloalkyl radical such as cyclohexyl, an aralkyl radical such as benzyl and an aryl radical such as phenyl and p-tolyl.

As isothiouronium groups there are meant groups which in one of their resonating forms may be represented by the formula ##STR5## wherein R⁸, R⁹, R¹⁰ and R¹¹ represent hydrogen atoms or hydrocarbon or substituted hydrocarbon radicals or R⁸ and R¹⁰ may together form an alkylene radical.

As examples of hydrocarbon and substituted hydrocarbon radicals which may be represented by R⁸, R⁹, R¹⁰ and R¹¹ there may be mentioned alkyl radicals such as methyl and ethyl, substituted alkyl radicals such as β-hydroxyethyl, cycloalkyl radicals such as cyclohexyl, aralkyl radicals such as benzyl and aryl radicals such as phenyl and p-tolyl. As an example of an alkylene radical which may be formed by R⁸ and R¹⁰ together there may be mentioned ethylene. In this case an imidazoline ring is formed.

As hydrazinium groups there are meant groups of the formula N⁺ R¹² R¹³ -NR¹⁴ R¹⁵ wherein R¹² represents an optionally substituted alkyl, cycloalkyl, aralkyl or phenyl radical or together with R¹³ and the adjacent nitrogen atom a heterocyclic system.

R¹³ represents an optionally substituted alkyl, cycloalkyl aralkyl or phenyl radical or together with R¹² and the adjacent nitrogen atom a heterocyclic system.

R¹⁴ represents a hydrogen atom or an optionally substituted alkyl radical or an acyl radical which may form a ring with R¹⁵ and N or when R¹² and R¹³ are other than phenyl, a phenyl radical.

R¹⁵ represents a hydrogen atom or an optionally substituted alkyl radical or an acyl radical.

As phosphonium groups there are meant groups of the formula ##STR6## wherein R¹⁶, R¹⁷ and R¹⁸ are organic radicals, which may be the same or different, each having a carbon atom linked directly to the phosphorus atom. As examples of organic radicals which may be represented by R¹⁶, R¹⁷ and R¹⁸ there may be mentioned aliphatic radicals, for example methyl, ethyl, propyl, butyl, allyl, chloromethyl, hydroxymethyl and δ-hydroxymethyl, aromatic radicals, for example, phenyl, naphthyl, p-chlorophenyl, aralkyl radicals, for example benzyl and heterocyclic radicals, for example -2-thienyl.

Particularly preferred cationic groups are cyclammonium groups especially pyridinium and ring methyl substituted pyridinium groups, i.e. α-, β- and γ-picolinium.

The anion X⁻ may be any anion of an inorganic or organic acid capable of forming a salt with a quaternary nitrogen cation.

Examples of the anion X⁻ include inorganic anions such as chloride, bromide, iodide, tetrachlorozincate, bisulphate, nitrate, sulphate, sulphamate, phosphate, borate, tetrafluoroborate, perchlorate, phosphomolybdate and organic ions such as acetate, propionate, oxalate, maleate, lactate, succinate, chloroacetate, benzoate, methyl sulphate, p-tolyl sulphonate and methane sulphonate. In the cases where the anion is polyvalent the dyestuff will contain a corresponding polar proportion of the cationic part of the dyestuff.

The ring A may carry additional substituents or have a benz ring fused thereon.

Examples of additional substituents which may be present in the ring A include halogen atoms for example chloro, bromo and fluoro, alkoxy for example methoxy and ethoxy, alkyl for example methyl, acylamino for example acetylamino, alkoxycarbonyl for example methoxycarbonyl, nitro, acyloxy for example acetoxy, aryloxy for example phenoxy, carbamyl for example diethylaminocarbonyl, amino for example methylamino, alkylsulphonyl, phenoxy sulphonyl, trifluoromethyl, alkoxycarbonylamino, dialkylaminosulphamyl, monoalkylaminosulphamyl, sulphamyl, acyl for example acetyl, cyano, arylazo, aryl for example phenyl, substituted aryl for example 4[2'-hydroxy-3-pyridinium-4'-methylpyrid-6'-one-5'-ylazo]-3-alkoxycarbonylphenyl.

A benz ring may be fused on to the ring A in the 3,4; 4,5 or 5,6 positions relative to the azo group as 1 but this will clearly depend on the position of Y.

A preferred class of dyestuffs is that wherein Y is --OCOR² where R² is an alkyl group of more than 5 carbon atoms and K⁺ is a cyclammonium or quaternary ammonium group.

Particularly preferred are those dyestuffs wherein Y is as defined in the previous paragraph, R is methyl, R¹ is hydrogen or lower alkyl preferably methyl and K⁺ is a pyridinium or methyl ring substituted pyridinium group.

As a further feature of the present invention there is provided a process for the manufacture of the dyestuffs of the invention which comprises diazotising an aromatic amine of the formula ##STR7## and coupling the diazonium salt with a pyridone of the formula ##STR8## wherein A, Y, R, R¹, K⁶¹ and X.sup.⊖ are as hereinbefore defined.

The diazotisation and coupling steps of the process may be carried out in conventional manner, for example by mixing a solution of the diazotised amine, obtained in known manner, with an aqueous solution of the coupling component.

Examples of aromatic amines which may be used as the diazo component include

4-benzoyloxy-aniline

2-nitro-4-benzoyloxy-aniline

4-acetylaniline

4-valeryloxyaniline

2-benzoyloxyaniline

4-capryloxy-aniline

4-lauryloxy aniline

4-stearyloxy-aniline

4-p-methyl benzoyloxyaniline

4-p-chlorobenzoyloxyaniline

4-phenylsulphonyloxyaniline

4-p-toluenesulphonyloxyaniline

4-nonylsulphonyloxy-aniline

4-dodecylsulphonyloxy aniline

4-hexadecylsulphonyloxy-aniline

4-nonylsulphonamido-aniline

4-dodecylsulphonamido-aniline

4-p-toluenesulphonamido-aniline

Examples of pyridone coupling components which may be used include:

2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1,2'-4-trimethyl-2-keto-3-pyridinium chloride-6-hydroxy-1,2-dihydropyridine,

1-(3"-methoxy)-n-propyl-2-keto-3-(2'-chloro)-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-n-butyl-2-keto-3-(4'-ethyl)-pyridinium chloride-4-methyl-6-hydroxy-1,2-pyridine,

1-(2"-ethylhexyl)-2-keto-3-(3'-cyano)-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2"-hydroxy)-ethyl-2-keto-3-(2'-methoxy)-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2"-N'"-methylpiperazinyl)-ethyl-2-keto-3-(2'-methyl)-pyridinium chloride-4-ethoxycarbonyl-6-hydroxy-1,2-dihydropyridine,

1-(2"-hydroxyethylamino)-ethyl-2-keto-3-(3'-methyl)-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2"-ethyl)-hexyl-2-keto-3-quinolinium chloride-4-methyl-6-hydroxy-1,2-pyridine,

1-methyl-2-keto-3-isoquinolinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-phenyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2"-chloro)-phenyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(3"-methyl)-phenyl-2-keto-3(2'-methyl)-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-dimethylamino-2-keto-3-β-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-amino-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-pyrrolidinyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(N-methyl)-piperazinyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-morpholinyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(4'-dimethylamino)-phenyl-2-keto-3(2"-methyl)-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-amino-2-keto-3-pyridinium chloride-4-ethoxycarbonyl-6-hydroxy-1,2-dihydropyridine,

1-dimethylamino-2-keto-3-pyridinium chloride-4-phenyl-6-hydroxy-1,2-dihydropyridine,

1-(3'-dibutylamino)-n-propyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2'-diethylamino)-ethyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2'-hydroxyethylamino)-ethyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-[2'-(2"-hydroxyethoxy)-ethylamino]-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2'-morpholinyl)-ethyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-(2'-N-methylpiperazinyl)-ethyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-pyridinium chloride-4-ethoxycarbonyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-pyridinium chloride-4-N",N"-dimethylcarbamoyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-pyridinium chloride-4-phenyl-6-hydroxy-1,2-dihydropyridine,

1-ethyl-2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-methyl-2-keto-3-trimethylammonium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-dimethylbenzylammonium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

1-ethyl-2-keto-3-[N-methyl-1-piperidinium chloride]-4-methyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-[N-methyl-1'-pyrrolidinium chloride]-4-methyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-[N-methyl-1'-morpholinium chloride]-4-methyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-dimethylsulphonium chloride-4-ethyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-dimethylhydrazinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine,

2-keto-3-trimethylphosphonium chloride-4-methyl-5-hydroxy-1,2-dihydropyridine.

An anion present in a dyestuff of the invention may be replaced by a different anion by known methods, for example, by metathesis.

An alternative method of producing the dyestuffs of the invention is by diazotising an amine of the formula ##STR9## and coupling the diazo compound with an acyl acetic ester for example ethyl acetoacetate, by known methods and then reacting the product with a salt of an acetic acid amide containing a cationic group, in the presence of a catalyst and a solvent such as methanol.

The dyestuffs of the invention are valuable for the colouration of synthetic polymeric materials by applicaton from an aqueous bath. The dyestuffs have a rapid rate of dyeing and may therefore be advantageously used in admixture with known commercial dyestuffs. The present dyestuffs give valuable bright shades of high tinctorial strength.

In particular the dyestuffs of the invention are valuable for colouring polyacrylonitrile materials and may be applied thereto from acid, neutral or slightly alkaline dyebaths (i.e. pH from 3-8) at temperatures between, for example, 40° C. and 120° C., preferably between 80° C. and 120° C. or by printing techniques using thickened printing pastes. Bright yellow to orange dyeings of excellent fastness properties to washing, perspiration, steam-pleating and light are obtained.

The preferred dyestuffs of the invention, that is those dyestuffs in which Y contains an alkyl group of more than 5 carbon atoms, possess a further advantage in that they have compatiblity values in the range 2.5 to 3.5, i.e. about 3 as assessed by the method for the determination of compatibility values described in the Journal of the Society of Dyers and Colourists, Volume 87, No. 2, page 60 (1971). Compatibility is assessed on a scale of 1 to 5 and dyers engaged in the dyeing of polyacrylonitrile materials show a strong preference for dyestuffs having a compatibility value or C.V. value as it is known, of 2.5 to 3.5. Additionally, dyestuffs of C.V. 2.5 to 3.5 are compatible in dyeing properties with the large majority of mainstream commercial dyes used in the dyeing of polyacrylonitrile.

The dyestuffs may also be used for the colouration of synthetic polymeric materials particularly polyacrylonitrile materials by wet transfer printing processes in which a support such as paper, is printed with an ink containing the dyestuff, the printed support is placed in contact with a textile material and the whole then subjected to heat and pressure under humid/wet conditions to transfer the dyestuff to the textile material.

The invention is illustrated by the following examples in which all parts and percentages are by weight except where otherwise indicated.

EXAMPLE 1

2.6 Parts of 2-nitro-4-benzoyloxyaniline is stirred with 10 parts of glacial acetic acid and 2.5 parts of concetrated hydrochloric acid. 5 Parts of 2N sodium nitrite are then added whilst maintaining the temperature at 0°-5° C. and the mixture is stirred at 0°-5° C. for 1/2 hour. Excess of nitrous acid is removed by the addition of a few drops of 20% sulphamic acid solution. A solution of 2.4 parts of 2-keto-3-pyridinium chloride-4-methyl-6-hydroxy-1,2-dihydropyridine in 75 parts of water is stirred at 0°-5° C. and the above diazo solution is then added over 10 minutes. After stirring for 1 hour at room temperature salt is added to 5% weight/volume and the mixture is then stirred for 15 minutes. The bright yellow solid is filtered off and washed with 25 parts of 5% brine then dried at 60° to yield an orange powder which dyes polyacrylonitrile and acrylonitrile co-polymer in vivid yellow shades of good light fastness and wash fastness and has the structure (I). ##STR10##

Further dyestuffs dyeing polyacrylonitrile in mid-yellow shades are obtained by similar methods and are described in the following table. The first column shows the diazo component corresponding to D NH₂, the second column shows the substituent R¹ and the third column the substituent K⁺. The anion is shown in the final column. The general formula of the dyestuff of Examples 2 to 7 is shown above the table. ##STR11##

    __________________________________________________________________________     Ex.                                                                               Diazo Component                                                             No.                                                                               corresponding to DNH.sub.2                                                                         R.sup.1                                                                           K.sup.⊕ X.sup.⊖                          __________________________________________________________________________                            H                                                                                  ##STR12##  Cl.sup.⊕                             3                                                                                  ##STR13##          C.sub.2 H.sub.5                                                                   "           SO.sub.4.sup.2-                          4                                                                                  ##STR14##          H                                                                                  ##STR15##  Cl.sup.⊖                         5                                                                                  ##STR16##          "  "           "                                        6  "                   C.sub.2 H.sub.5                                                                   "           "                                        7  "                   "                                                                                  ##STR17##  "                                        __________________________________________________________________________

further dyestuffs dyeing polyacrylonitrile in the shades shown in the final column are described in the following table. The first column shows the diazo component corresponding to DNH₂, the second column shows the substituent R¹ and the third column the substituent K.sup.⊕. The anion is shown in the fourth column. The general formula of the dyestuff of the examples is shown above the table. ##STR18##

    __________________________________________________________________________                                            Shade imparted                             Diazo Component                     to acrylic                              Ex.                                                                               corresponding to DNH.sub.2                                                                    R.sup.1 K.sup.⊕                                                                           A.sup.⊖                                                                      fibres                                  __________________________________________________________________________      8 3-benzoyloxy aniline                                                                          H       pyridinium                                                                            CH.sub.3 COO.sup.⊖                                                           greenish-yellow                          9 4-capryloxy aniline                                                                           H       pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                              10 4-capryloxy aniline                                                                           CH.sub.3                                                                               α-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                              11 4-phenylsulphonyloxyaniline                                                                   H       α-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                              12 4-phenylsulphonyloxyaniline                                                                   CH.sub.3                                                                               pyridinium                                                                            1/2SO.sub.4.sup.2⊖                                                           mid-yellow                              13 2-nitro-4-phenylsulphonyloxy-                                                                 H       pyridinium                                                                            1/2SO.sub.4.sup.2⊖                                                           mid-yellow                                 aniline                                                                     14 2-nitro-4-phenylsulphonyloxy-                                                                 C.sub.4 H.sub.9                                                                        pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                                 aniline                                                                     15 4-capryloxy aniline                                                                           nC.sub.4 H.sub.9                                                                       pyridinium                                                                            CH.sub.3 COO.sup.⊖                                                           mid-yellow                              16 4-p-toluenesulphonyloxy-                                                                      H       pyridinium                                                                            CH.sub.3 COO.sup.⊖                                                           mid-yellow                                 aniline                                                                     17 4-p-toluenesulphonyloxy-                                                                      CH.sub.3                                                                               γ-picolinium                                                                    Br.sup.⊖                                                                     mid-yellow                                 aniline                                                                     18 4-p-toluenesulphonamido-                                                                      CH.sub.3                                                                               γ-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                                 aniline                                                                     19 2-nitro-4-benzoyloxy aniline                                                                  CH.sub.3                                                                               pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                              20 2-nitro-4-benzoyloxy aniline                                                                  nC.sub.4 H.sub.9                                                                       pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                              21 3-benzoyloxy aniline                                                                          CH.sub.3                                                                               γ-picolinium                                                                    Cl.sup.⊖                                                                     greenish-yellow                         22 4-p-toluenesulphonamido- aniline                                                                      γ-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                              23 4-p-toluenesulphonamido- aniline                                                               ##STR19##                                                                             pyridinium                                                                            CH.sub.3 COO.sup.⊖                                                           mid-yellow                              24 4-p-toluenesulphonamido-                                                                      NH.sub.2                                                                               pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                                 aniline                                                                     25 3-p-toluenesulphonyloxy-                                                                      nC.sub.4 H.sub.9                                                                       pyridinium                                                                            Cl.sup.⊖                                                                     greenish-yellow                            aniline                                                                     26 3-benzoyloxy aniline                                                                          nC.sub.4 H.sub.9                                                                       pyridinium                                                                            1/2SO.sub.4.sup.2⊖                                                           greenish-yellow                         27 3-benzoyloxy aniline                                                                           ##STR20##                                                                             α-picolinium                                                                    Cl.sup.⊖                                                                     greenish-yellow                         28 3-benzoyloxy aniline                                                                          H       γ-picolinium                                                                    Cl.sup.⊖                                                                     greenish-yellow                         29 4-phenylsulphonyloxy- aniline                                                                  ##STR21##                                                                             γ-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                              30 4-phenylsulphonyloxy- aniline                                                                  ##STR22##                                                                             γ-picolinium                                                                    CH.sub.3 COO.sup.⊖                                                           mid-yellow                              31 3-p-toluenesulphonyloxy- aniline                                                               ##STR23##                                                                             γ-picolinium                                                                    CH.sub.3 COO.sup.⊖                                                           greenish-yellow                         32 3-(β-naphthoyloxy)aniline                                                                H       pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                              33 3-(β-naphthoyloxy)aniline                                                                CH.sub.3                                                                               γ-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                              34 3-(β-naphthoyloxy)aniline                                                                nC.sub.4 H.sub.9                                                                       α-picolinium                                                                    CH.sub.3 COO.sup.⊖                                                           mid-yellow                              35 4-p-toluenesulphonyloxy- aniline                                                               ##STR24##                                                                             α-picolinium                                                                    CH.sub.3 COO.sup.⊖                                                           mid-yellow                              36 4-p-toluenesulphonyloxy-                                                                      CH.sub.3                                                                               pyridinium                                                                            Cl.sup.⊖                                                                     mid-yellow                                 aniline                                                                     37 4-(β-naphthoyloxy)aniline                                                                H       α-picolinium                                                                    SO.sub.2 NH.sup.⊖                                                            mid-yellow                              38 4-(β-naphthoyloxy)aniline                                                                NH.sub.2                                                                               α-picolinium                                                                    Cl.sup.⊖                                                                     mid-yellow                              __________________________________________________________________________ 

We claim:
 1. An azo dyestuff devoid of carboxylic acid and sulphonic acid groups and of the formula ##STR25## wherein R is methyl, R¹ is hydrogen or lower alkyl, Y is a group --OCOR² wherein R² is aryl or alkyl or more than 5 carbon atoms, K.sup.⊕ is a pyridinium or methyl ring substituted pyridinium group and X.sup.⊖ is an anion.
 2. An azo dyestuff as claimed in claim 1 wherein the group Y is in the para position relative to the azo group. 